A self-moisture-absorbing membrane material and its preparation method

Abstract

This application relates to the field of packaging films, and in particular to a self-absorbing moisture-absorbing film material and its preparation method. The self-absorbing moisture-absorbing film material comprises, from the outside to the inside, a corona layer, a barrier layer, and a moisture-absorbing layer. The barrier layer uses a combination of high-moisture-barrier HDPE and processable LDPE and LLDPE, resulting in good barrier properties, flexibility, tensile strength, and durability. A desiccant is incorporated into the moisture-absorbing layer, which absorbs moisture from inside the packaging or permeates through the barrier layer. The combination of a barrier layer with high barrier properties and a moisture-absorbing layer with good moisture absorption properties in the self-absorbing moisture-absorbing film material results in packaging bags with excellent barrier performance.

Description

Technical Field

[0001] This application relates to the field of packaging films, and in particular to a self-moisture-absorbing film material and its preparation method. Background Technology

[0002] Packaging materials are the general term for materials used to manufacture packaging containers and constitute product packaging. They are the material basis for product packaging and the material carrier of packaging functions. Packaging materials generally need to have good mechanical properties, stability, adhesiveness, and heat-sealing properties. For packaging of moisture-absorbing items such as milk powder, puffed food, salt, flour, pharmaceuticals, and biological testing reagents, in addition to the above properties, they should also have barrier properties, that is, they should block oxygen, water vapor, and other substances in the air to prevent the contents from absorbing moisture and deteriorating.

[0003] Currently, to prevent the contents of packaging bags from absorbing moisture and deteriorating, individual desiccants are usually placed in the film bag to ensure the dryness inside the bag. However, existing general packaging bags have poor water vapor and oxygen permeability, so individual desiccants cannot effectively absorb moisture, resulting in unsatisfactory drying effects. Moreover, individual desiccants pose a risk of accidental ingestion. Summary of the Invention

[0004] To address the problem of poor water vapor and oxygen permeability in existing packaging films, this application provides a self-absorbing moisture film material and its preparation method.

[0005] In one aspect, this application provides a self-absorbing moisture membrane material.

[0006] 1. A self-absorbing moisture membrane material, comprising a corona layer, a barrier layer, and a moisture-absorbing layer in sequence; the corona layer is composed of 20-60 parts by weight of LDPE and 40-80 parts by weight of LLDPE; the barrier layer is composed of 10-20 parts by weight of LDPE, 10-20 parts by weight of LLDPE, and 60-80 parts by weight of HDPE; the moisture-absorbing layer is composed of 20-60 parts by weight of LDPE, 20-50 parts by weight of LLDPE, and 10-30 parts by weight of a desiccant; the desiccant is a substance with a moisture absorption rate ≥20%.

[0007] By adopting the above technical solutions, a corona layer is set in the self-absorbing moisture film material. The corona layer can be corona treated, so that the surface of the corona layer of the self-absorbing moisture film material has more active groups (such as hydroxyl and carboxyl groups), thereby having higher adhesion performance and facilitating the adhesion of other layers (such as printing layers and / or protective layers). A barrier layer is set in the self-absorbing moisture film material. The barrier layer uses HDPE with good moisture resistance and LDPE and LLDPE with good processing performance, so that the prepared barrier layer has good moisture resistance, flexibility, tensile properties and strength. A desiccant is set in the moisture-absorbing layer. The desiccant can absorb moisture inside the packaging or through the barrier layer. The combination of a barrier layer with high barrier performance and a moisture-absorbing layer with good moisture absorption performance in the self-absorbing moisture film material makes the packaging bag made from the self-absorbing moisture film material have excellent barrier performance.

[0008] Preferably, the hygroscopic agent is at least one of the following: micronized silica gel, zeolite, calcium oxide, lithium chloride, calcium chloride, magnesium chloride, aluminum chloride, sodium sulfate, calcium sulfate, magnesium sulfate, zinc sulfate, potassium acetate, dimethylamine hydrochloride, orthophosphoric acid, guanidine hydrochloride, guanidine phosphate, guanidine aminosulfonate, guanidine hydroxymethyl phosphate, guanidine carbonate, potassium hydroxide, sodium hydroxide, and magnesium hydroxide.

[0009] By adopting the above technical solution, the desiccant adsorbs moisture through chemical or physical means, giving the self-moisture-absorbing film material high moisture absorption performance, thereby improving the barrier performance of packaging bags using the self-moisture-absorbing film material.

[0010] Preferably, the desiccant is a composition of calcium chloride and micronized silica gel in a mass ratio of (2-3):1.

[0011] By adopting the above technical solution, the micronized silica gel has a porous adsorption structure with high moisture absorption rate, good film-forming properties and mechanical properties, and calcium chloride has a high moisture absorption rate. By optimizing the type and amount of desiccant, the self-moisture film material can simultaneously have excellent moisture absorption rate and mechanical properties, thereby improving the barrier performance of packaging bags using self-moisture film material.

[0012] Preferably, the moisture-absorbing layer has three layers.

[0013] By adopting the above technical solution, and by setting three moisture-absorbing layers, two membrane interfaces are formed between the three moisture-absorbing layers. The membrane interfaces help to reduce the passage of water vapor and oxygen, and help the moisture-absorbing layer close to the barrier layer to fully absorb water vapor, thereby reducing the amount of water vapor entering the packaging. This can improve the moisture absorption rate of the self-absorbing film material, and thus improve the barrier performance of the packaging bag using the self-absorbing film material.

[0014] Preferably, the raw material of the moisture-absorbing layer further includes 5-10 parts by weight of polydimethylsiloxane and 5-10 parts by weight of paraffin.

[0015] By adopting the above technical solution, polydimethylsiloxane agent and paraffin are added to the moisture-absorbing layer. The polydimethylsiloxane agent and paraffin migrate to the surface of the moisture-absorbing layer and form a hydrophobic barrier film. The addition of polydimethylsiloxane agent and paraffin to the moisture-absorbing layer and the setting of three layers enhance the barrier of the moisture-absorbing layer against water vapor and oxygen, promote the full absorption of water vapor by the moisture-absorbing layer near the barrier layer, thereby reducing the water vapor and oxygen entering the packaging, further improving the moisture absorption rate of the self-absorbing film material, and thus improving the barrier performance of the packaging bag using the self-absorbing film material.

[0016] Preferably, the raw material of the barrier layer further includes 0.5-1.5 parts by weight of talc powder.

[0017] By adopting the above technical solution, talc powder is used in the barrier layer as a nucleating agent to promote the growth of crystal nuclei in the barrier layer, improve the crystallinity of the barrier layer, enhance the strength and barrier performance of the barrier layer, and thus improve the barrier performance of packaging bags using self-absorbing moisture film materials.

[0018] Preferably, the self-moisture-absorbing membrane material is further provided with a protective layer, which is disposed on the side away from the barrier layer and corona layer; the protective liquid includes 15-30 parts by weight of nano-silica sol, 5-10 parts by weight of siloxane polyoxyethylene ether, 5-10 parts by weight of perfluorooctyl ethanol polyoxyethylene ether, 5-20 parts by weight of polyacrylate resin and 30-90 parts by weight of water.

[0019] By adopting the above technical solution, the protective layer reduces the surface energy of the self-absorbing moisture film material, which can improve the friction resistance, stain resistance, corrosion resistance and isolation performance of the self-absorbing moisture film material, as well as reduce the oxygen and water vapor transmission rate, thereby improving the barrier performance of packaging bags using self-absorbing moisture film material.

[0020] Preferably, the protective liquid further includes 3-6 parts by weight of nano-aluminum sol.

[0021] By adopting the above technical solution, the combination of nano-aluminum sol and nano-silica sol further enhances the barrier performance of the protective layer; and the positive charge in the aluminum sol has a good compatibility effect with the negative charge on the surface of the corona layer, which enhances the interaction force between the protective layer and the corona layer, further improving the protective effect of the protective layer on the corona layer, barrier layer and moisture-absorbing layer, and improving the barrier performance of packaging bags using self-moisture-absorbing film materials.

[0022] Preferably, the protective liquid further includes 0.5-1.5 parts by weight of a crosslinking agent; the crosslinking agent is 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane or γ-glycidyl ether propyltrimethoxysilane.

[0023] By adopting the above technical solution, the crosslinking agent can enhance the interaction force between raw materials in the protective liquid, enhance the cohesive force of the protective liquid forming the film layer, and thus improve the barrier performance of packaging bags using self-moisture film materials.

[0024] On the other hand, this application provides a method for preparing a self-moisture-absorbing membrane material:

[0025] A method for preparing a self-absorbing moisture membrane material: the raw materials of the corona layer, the barrier layer, and the moisture-absorbing layer are plasticized separately, then extruded to form sequentially stacked molten resins, and then the sequentially stacked molten resins are blown to obtain the self-absorbing moisture membrane material.

[0026] Preferably, the thickness of the corona layer, barrier layer and moisture-absorbing layer of the self-absorbing moisture membrane material is 0.08-0.15 mm; the thickness ratio of the corona layer, barrier layer and moisture-absorbing layer is 1:2:(2-3).

[0027] By adopting the above technical solution, a self-moistening film material with good barrier properties, moisture absorption properties, and mechanical properties is prepared. This results in packaging bags made from this self-moistening film material having excellent barrier and moisture absorption properties, and a long moisture protection period of over two years. This packaging bag eliminates the need for individually packaged desiccants, avoiding the risks of leakage and accidental ingestion associated with packaged desiccants, making it safer and more reliable. It also reduces production costs for customers using this packaging bag and is more environmentally friendly.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. A self-absorbing moisture-absorbing film material, comprising, from the outside to the inside, a corona layer, a barrier layer, and a moisture-absorbing layer; the barrier layer uses HDPE with good moisture barrier properties in combination with LDPE and LLDPE with good processing performance, so that the barrier layer has good barrier properties, flexibility, tensile properties, and strength; the moisture-absorbing layer contains a desiccant, which can absorb moisture inside the packaging or through the barrier layer. The self-absorbing moisture-absorbing film material uses a barrier layer with high barrier properties and a moisture-absorbing layer with good moisture absorption properties, so that the packaging bag made from the self-absorbing moisture-absorbing film material has excellent barrier properties.

[0030] 2. Furthermore, a three-layer moisture-absorbing layer is set up, and polydimethylsiloxane agent and paraffin are added to the moisture-absorbing layer to improve the barrier and moisture absorption performance of the moisture-absorbing layer; talc is added to the barrier layer to improve the crystallinity of the barrier layer and thus improve the barrier performance. The barrier layer and the moisture-absorbing layer work together to further improve the barrier performance of the packaging bag using self-moisture-absorbing film material.

[0031] 3. Furthermore, the self-absorbing moisture film material also includes a protective layer. The protective layer reduces the surface energy of the self-absorbing moisture film material, improves its resistance to friction, dirt, corrosion and isolation, and reduces the permeability of oxygen and water vapor, thereby improving the barrier performance of packaging bags using self-absorbing moisture film material. Detailed Implementation

[0032] raw material

[0033] LDPE (melt index 2g / 10min, density 0.926g / cm3), LLDPE (melt index 2g / 10min, density 0.921g / cm3), MDPE (density 0.940g / cm3, melt index (190℃ / 2.16kg) 0.90g / 10min), HDPE (density 0.958g / cm3, melt index 0.28g / 10min), paraffin wax (molecular weight 360-540), nano aluminum sol (solid content 25%, particle size 30nm), micronized silica gel (active ingredient 98%, average particle size 15μm), polyacrylate resin (carbomer 980, content 99%, industrial grade).

[0034] Example

[0035] Example 1: A self-absorbing moisture membrane material, which is provided with a corona layer, a barrier layer and a moisture-absorbing layer in sequence, the moisture-absorbing layer comprising 3 layers.

[0036] The preparation method of the self-moisture-absorbing membrane material is as follows:

[0037] The raw materials for the corona layer and the barrier layer are fed into the feed port of the blown film extruder single screw extruder and extruded into the die head through the single screw extruder.

[0038] The raw materials for the moisture-absorbing layer are first fed into a twin-screw extruder and uniformly mixed to form a mixture. The mixed material is then extruded into the feed inlet of the single-screw extruder of the blown film machine. After being plasticized by the single-screw extruder, it is extruded into the die head. The raw materials for the corona layer, barrier layer, and moisture-absorbing layer are plasticized and then composited at the die head to form molten resin (5 layers) stacked sequentially. Finally, the 5 layers of molten resin are blown by the die head to form a self-moisture-absorbing film material.

[0039] Corona layer: The temperatures of each zone of the single-screw extruder are as follows: Zone 1 180±5℃, Zone 2 185±5℃, Zone 3 190±5℃, Zone 4 195±5℃, Zone 5 190±5℃, Zone 6 190±5℃, and the die temperature is 195±5℃.

[0040] Barrier layer: The temperatures of each zone of the single screw extruder are as follows: Zone 1 190±5℃, Zone 2 195±5℃, Zone 3 198±5℃, Zone 4 200±5℃, Zone 5 195±5℃, Zone 6 195±5℃, and the die temperature is 190±5℃.

[0041] Moisture-absorbing layer: The temperature range of the twin-screw extruder is 190±10℃. The temperatures of each zone of the single-screw extruder are as follows: Zone 1 180±5℃, Zone 2 185±5℃, Zone 3 190±5℃, Zone 4 195±5℃, Zone 5 190±5℃, Zone 6 190±5℃. The die temperature is 195±5℃.

[0042] Blow molding process parameters: The internal cooling air intake frequency of the air cooler is 22±2Hz, the internal cooling air exhaust frequency is 27±3Hz, and compressed air is injected into the air inlet of the mold head. The blow-up ratio is controlled at 2.0±0.2, and the film bubble is pulled up at a uniform speed with a traction rope.

[0043] Examples 2 and 3 describe a self-moisture-absorbing membrane material. The difference between this material and Example 1 is that the weight and thickness of the raw materials used in the corona layer, barrier layer, and moisture-absorbing layer are different, as detailed in Table 1.

[0044] Table 1. List of weights and thicknesses of raw materials used in the corona layer, barrier layer, and moisture-absorbing layer of the self-absorbing moisture-absorbing membrane materials in Examples 1 to 3.

[0045]

[0046]

[0047] Example 4, a self-absorbing moisture-absorbing film material, differs from Example 1 in that the desiccant is a composition of calcium chloride and micronized silica gel in a mass ratio of 1:1.

[0048] Example 5, a self-absorbing moisture-absorbing membrane material, differs from Example 1 in that the desiccant is a combination of calcium chloride and micronized silica gel in a mass ratio of 2:1.

[0049] Example 6, a self-absorbing moisture-absorbing film material, differs from Example 1 in that the desiccant is a combination of calcium chloride and micronized silica gel in a mass ratio of 3:1.

[0050] Example 7, a self-absorbing moisture-absorbing membrane material, differs from Example 1 in that the desiccant is a combination of magnesium chloride and micronized silica gel in a mass ratio of 3:1.

[0051] Example 8, a self-absorbing moisture-absorbing film material, differs from Example 1 in that the desiccant is a combination of calcium sulfate and micronized silica gel in a mass ratio of 2:1.

[0052] Example 9, a self-absorbing moisture-absorbing film material, differs from Example 1 in that the desiccant is calcium chloride.

[0053] Example 10, a self-absorbing moisture membrane material, differs from Example 1 in that the raw materials of the moisture-absorbing layer also include 10 kg of polydimethylsiloxane and 5 kg of paraffin; the raw materials of the barrier layer also include 1.5 kg of talc.

[0054] Example 11, a self-absorbing moisture membrane material, differs from Example 1 in that the raw materials of the moisture-absorbing layer also include 5 kg of polydimethylsiloxane and 10 kg of paraffin; the raw materials of the barrier layer also include 0.5 kg of talc.

[0055] Example 12, a self-absorbing moisture membrane material, differs from Example 10 in that the moisture-absorbing layer uses 3 kg of polydimethylsiloxane and 3 kg of paraffin; the barrier layer uses 0.2 kg of talc.

[0056] Example 13, a self-absorbing moisture membrane material, differs from Example 10 in that the moisture-absorbing layer is not three layers, but one layer (the thickness of the one layer is the sum of the thicknesses of the three layers in Example 10).

[0057] Example 14, a self-absorbing moisture membrane material, differs from Example 10 in that talc is not used in the barrier layer of the moisture-absorbing layer.

[0058] Example 15, a self-absorbing moisture membrane material, differs from Example 10 in that polydimethylsiloxane is used to replace paraffin in an equal amount in the moisture-absorbing layer; and talc is not used in the barrier layer.

[0059] Example 16, a self-absorbing moisture membrane material, differs from Example 10 in that paraffin wax is used in an equal amount to replace polydimethylsiloxane in the moisture-absorbing layer; and talc is not used in the barrier layer.

[0060] Example 17, a self-absorbing moisture-absorbing membrane material, differs from Example 10 in that it does not use paraffin and polydimethylsiloxane in the moisture-absorbing layer. (Talc powder is used alone.)

[0061] Example 18, a self-absorbing moisture membrane material, differs from Example 1 in that the corona layer is corona treated using an online corona machine, and the surface tension of the corona layer after treatment is ≥40dyn; and the self-absorbing moisture membrane material is also provided with a protective layer, which is located on the side away from the barrier layer corona layer. The protective layer is prepared by spraying a protective liquid (using raw materials as shown in Table 2) onto the outside of the corona layer and then drying it at 65°C for 8 minutes.

[0062] Examples 19 and 20 describe a self-moisture-absorbing membrane material, which differs from Example 18 in that the raw materials used for the protective liquid, the drying conditions for the protective liquid forming the membrane layer, and the thickness are different.

[0063] Table 2 lists the raw materials of the protective liquid used in the self-moisture-absorbing membrane materials of Examples 18 to 20, as well as the drying conditions and thickness settings for the protective liquid forming the film layer.

[0064]

[0065]

[0066] Example 21, a self-moisture-absorbing membrane material, differs from Example 18 in that the corona layer is not corona-treated.

[0067] Example 22, a self-absorbing moisture membrane material, differs from Example 18 in that it uses an equal amount of fatty alcohol polyoxyethylene ether AEO-9 to replace perfluorooctyl ethanol polyoxyethylene ether; and does not use a crosslinking agent.

[0068] Example 23, a self-moisture-absorbing membrane material, differs from Example 18 in that octadecyl dimethyl betaine is used to replace siloxane polyoxyethylene ether in an equal amount; and nano-aluminum sol is not used.

[0069] Example 24, a self-moisture-absorbing membrane material, differs from Example 18 in that it does not use nano-aluminum sol and crosslinking agent.

[0070] Comparative Example

[0071] Comparative Example 1, a self-absorbing moisture membrane material, differs from Example 1 in that the corona layer uses 50 kg LDPE, 40 kg metallocene polyethylene and 10 kg HDPE; the barrier layer uses 25 kg LDPE, 35 kg metallocene polyethylene and 10 kg HDPE; and the moisture-absorbing layer uses 50 kg LDPE, 40 kg metallocene polyethylene and 10 kg HDPE.

[0072] Comparative Example 2, a self-absorbing moisture membrane material, differs from Example 1 in that the barrier layer uses 25 kg of LDPE, 25 kg of LLDPE, and 50 kg of HDPE; and the moisture-absorbing layer uses 8 kg of desiccant.

[0073] Comparative Example 3, a self-moisture-absorbing membrane material, differs from Example 1 in that the barrier layer uses 8 kg of LDPE, 8 kg of LLDPE, and 85 kg of HDPE; and the moisture-absorbing layer uses 8 kg of desiccant.

[0074] Comparative Example 4 is a self-absorbing moisture-absorbing membrane material, which differs from Example 1 in that no desiccant is used in the moisture-absorbing layer.

[0075] Performance testing

[0076] Experiment 1: Water vapor transmission rate

[0077] The water vapor transmission rate of the test sample was tested according to GB / T1037-2021, at a temperature of 38℃ and a humidity of 90%RH.

[0078] Experiment 2: Oxygen Transmission Rate

[0079] The oxygen permeability of the test sample was tested according to GB / T 19789-2021, at a temperature of 23℃ and a humidity of 0%RH.

[0080] Test 3: Puncture resistance

[0081] The puncture resistance of the test samples was tested according to GB / T 37841-2019.

[0082] Test samples: The self-absorbing moisture-absorbing membrane materials of Examples 1 to 24 were used as example samples, and the self-absorbing moisture-absorbing membrane materials of Comparative Examples 1 to 4 were used as comparative example samples.

[0083] Test results: The water vapor transmission rate, oxygen transmission rate and puncture resistance of the self-moisture-absorbing membrane materials of Examples 1 to 24 and Comparative Examples 1 to 4 are shown in Table 3.

[0084] Experiment 4: Clumping of packaging bags after 90 and 150 days

[0085] Examples 1 to 23 and Comparative Examples 1 to 4 used self-absorbing moisture-absorbing membrane materials to prepare identical sealed packaging bags containing 500g of anhydrous citric acid granules (the volume of the anhydrous citric acid granules was approximately half the volume of the packaging bag, with N=3 samples per test). The bags were placed at a test temperature of 25°C and a humidity of 80% RH for 90 and 150 days, and the clumping of the anhydrous citric acid granules in the packaging bags was observed. 1- No clumping (no clumping in any of the 3 samples); 2- Slight clumping (at least one of the 3 samples showed slight clumping); 3- Significant clumping (at least two of the 3 samples showed significant clumping); 4- Complete clumping (at least two of the 3 samples showed complete clumping). The test results are shown in Table 3.

[0086] Table 3 lists the evaluation results of water vapor transmission rate, oxygen transmission rate, puncture resistance, and clumping of the self-absorbing membrane materials of Examples 1 to 24 and Comparative Examples 1 to 4 after 90 and 150 days of sealed packaging.

[0087]

[0088]

[0089] Combining Examples 1 to 24 and Comparative Examples 1 to 4, and referring to Table 3, it can be seen that:

[0090] Compared to Comparative Examples 1 to 4, the self-absorbing moisture-absorbing film materials of Examples 1 to 24 have lower water vapor permeability and oxygen permeability. The packaging bags prepared using this self-absorbing moisture-absorbing film material have better barrier properties (90 days and 150 days), possibly because the self-absorbing moisture-absorbing film material uses a barrier layer and a moisture-absorbing layer. The barrier layer uses HDPE with good moisture barrier properties in combination with LDPE and LLDPE with good processing properties, which gives the barrier layer good barrier properties, flexibility and strength. The moisture-absorbing layer contains a desiccant, which can absorb moisture inside the packaging or permeate through the barrier layer. The self-absorbing moisture-absorbing film material uses a barrier layer with high barrier properties and a moisture-absorbing layer with good moisture absorption properties, which makes the packaging bags prepared using the self-absorbing moisture-absorbing film material have excellent barrier properties.

[0091] Compared with Examples 1 to 4 and Examples 7 to 9, the self-absorbing moisture membrane materials of Examples 5 to 6 have both lower water vapor permeability and higher puncture resistance, indicating that the desiccant is a combination of calcium chloride and micronized silica gel with a mass ratio of (2-3):1, which reduces the water vapor permeability of the self-absorbing moisture membrane material and also has higher puncture resistance.

[0092] The reasons for this may be as follows: Micronized silica gel has a porous adsorption structure and a high moisture absorption rate, exhibiting good dispersibility and film-forming properties in the membrane layer, resulting in a self-moisture-absorbing membrane material with good mechanical properties; calcium chloride has a very high moisture absorption rate (generally ≥200%) and becomes gel-like after absorbing moisture, resulting in good adhesion to the membrane layer and increased membrane density, further enhancing the membrane layer's barrier properties against oxygen and water vapor. By optimizing the type and amount of desiccant, the self-moisture-absorbing membrane material can simultaneously possess excellent moisture absorption rate and puncture resistance, thereby improving the barrier performance of packaging bags using self-moisture-absorbing membrane materials.

[0093] Although the self-absorbing moisture membrane material of Example 9 has a low water vapor permeability, its puncture resistance is also low. This may be because although calcium chloride has a high moisture absorption rate, the calcium chloride is in granular form before moisture absorption and the bonding force between it and PE is weak. A high calcium chloride content will cause internal defects in the self-absorbing moisture membrane material, resulting in a decrease in the puncture resistance of the self-absorbing moisture membrane material.

[0094] Compared to Examples 1 to 3 and Examples 12 to 17, the self-absorbing moisture-absorbing film materials of Examples 10 to 11 have lower water vapor permeability and oxygen permeability, and higher puncture resistance. After 150 days, the anhydrous citric acid particles in the packaging bags prepared using the self-absorbing moisture-absorbing film materials of Examples 10 to 11 do not clump. Compared to Examples 1 to 3, the self-absorbing moisture-absorbing film materials of Examples 10 to 17 have lower water vapor permeability and oxygen permeability, and higher puncture resistance. This indicates that by setting three moisture-absorbing layers in the self-absorbing moisture-absorbing film material, adding polydimethylsiloxane and paraffin to the moisture-absorbing layers, and adding talc to the barrier layers, the water vapor permeability and oxygen permeability of the self-absorbing moisture-absorbing film material are reduced, and the puncture resistance is improved. Consequently, the packaging bags made from the prepared self-absorbing moisture-absorbing film material have better barrier properties.

[0095] The reason for this may be that the polydimethylsiloxane agent and paraffin improve the dispersion performance of the raw materials in the moisture-absorbing layer, thereby improving the mechanical properties and puncture resistance of the moisture-absorbing layer. A three-layer moisture-absorbing structure is thus implemented.

[0096] Polydimethylsiloxane and paraffin migrate to the surface of the moisture-absorbing layer, forming a hydrophobic barrier film. This enhances the barrier against water vapor and oxygen, promoting the absorption of water vapor by the moisture-absorbing layer near the barrier, thereby reducing the amount of water vapor and oxygen entering the packaging. The use of talc in the barrier layer acts as a nucleating agent, promoting the growth of crystal nuclei within the barrier layer and increasing its crystallinity. This, in turn, improves the barrier layer's strength, puncture resistance, and barrier performance. The combined use of the barrier layer and the moisture-absorbing layer reduces the water vapor and oxygen permeability of the self-absorbing film material, improves puncture resistance, and ultimately enhances the barrier performance of packaging bags using self-absorbing film material.

[0097] Compared to Examples 1 to 3 and Examples 21 to 24, the self-absorbing moisture-absorbing film materials of Examples 18 to 20 have lower water vapor permeability and oxygen permeability, and higher puncture resistance. After 150 days, the anhydrous citric acid particles in the packaging bags prepared using the self-absorbing moisture-absorbing film materials of Examples 18 to 20 do not clump, indicating that the protective layer of the self-absorbing moisture-absorbing film material reduces the water vapor permeability and oxygen permeability of the self-absorbing moisture-absorbing film material, improves the puncture resistance of the self-absorbing moisture-absorbing film material, and thus improves the barrier performance of the packaging bags prepared using the self-absorbing moisture-absorbing film material.

[0098] The reason for this may be that the protective layer on the self-absorbing moisture film material reduces the surface energy of the self-absorbing moisture film material, improves its resistance to friction, dirt, corrosion and isolation, and reduces the permeability of oxygen and water vapor, thereby improving the barrier performance of packaging bags using self-absorbing moisture film material.

[0099] The protective liquid raw materials utilize perfluorooctyl ethanol polyoxyethylene ether and siloxane polyoxyethylene ether, which have low surface energy. This not only ensures good dispersion of latex particles in the protective liquid but also reduces the surface energy of the protective layer. The use of nano-aluminum sol and nano-silica sol in the protective liquid raw materials enhances the abrasion resistance, stain resistance, corrosion resistance, strength, and barrier properties of the self-absorbing moisture membrane material. Furthermore, the positive charge in the aluminum sol has a good compatibility with the negative charge on the corona layer surface, reducing the migration of the smaller molecular weight perfluorooctyl ethanol polyoxyethylene ether and siloxane polyoxyethylene ether in the protective layer. This, in turn, improves the protection of the corona layer, barrier layer, and moisture-absorbing layer. Consequently, the moisture-absorbing membrane material exhibits low water vapor and oxygen permeability, high puncture resistance, and excellent barrier properties in packaging bags prepared using the self-absorbing moisture membrane material.

[0100] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A self-absorbing moisture-absorbing film material, characterized in that, The material comprises a corona layer, a barrier layer, and a moisture-absorbing layer, arranged sequentially. The corona layer is composed of 20-60 parts by weight of LDPE and 40-80 parts by weight of LLDPE. The barrier layer is composed of 10-20 parts by weight of LDPE, 10-20 parts by weight of LLDPE, and 60-80 parts by weight of HDPE. The moisture-absorbing layer is composed of 20-60 parts by weight of LDPE, 20-50 parts by weight of LLDPE, and 10-30 parts by weight of a desiccant. The desiccant is a substance with a moisture absorption rate ≥20%. The desiccant is a composition of calcium chloride and micronized silica gel in a mass ratio of (2-3):1; The moisture-absorbing layer has three layers; The raw materials for the moisture-absorbing layer also include 5-10 parts by weight of polydimethylsiloxane and 5-10 parts by weight of paraffin. The raw material of the barrier layer also includes 0.5-1.5 parts by weight of talc powder.

2. The self-moisture-absorbing membrane material according to claim 1, characterized in that, The self-absorbing moisture membrane material is further provided with a protective layer, which is disposed on the side of the corona layer away from the barrier layer; the protective layer is prepared by spraying a protective liquid onto the outside of the corona layer; the protective liquid includes 15-30 parts by weight of nano-silica sol, 5-10 parts by weight of siloxane polyoxyethylene ether, 5-10 parts by weight of perfluorooctyl ethanol polyoxyethylene ether, 5-20 parts by weight of polyacrylate resin and 30-90 parts by weight of water.

3. The self-absorbing moisture-absorbing membrane material according to claim 2, wherein the protective liquid further comprises 3-6 parts by weight of nano-aluminum sol.

4. The self-absorbing moisture-absorbing membrane material according to claim 2, wherein the protective liquid further comprises 0.5-1.5 parts by weight of a crosslinking agent; the crosslinking agent is 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane or γ-glycidyl ether propyltrimethoxysilane.

5. A method for preparing the self-moisture-absorbing membrane material according to any one of claims 1-4, characterized in that, The preparation steps include the following: The raw materials for the corona layer, the barrier layer, and the moisture-absorbing layer are plasticized separately, then extruded to form sequentially stacked molten resins. Finally, the sequentially stacked molten resins are blown to prepare a self-moisture-absorbing membrane material.

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